There are several problems as I see related to urban sprawl. The largest of which is not government planning, but rather popular expectations of government. Urban sprawl that occurs naturally, is not a negative. That is where those who choose to move out, away from the conveniences of the city, do so knowing that the conveniences will be lost, or have to be paid for at their true market values. This has not been the case.
Urban planners, first drive out people who want to keep the freedom they were accustomed to on private property in the cit.y. They then demand increased service that they are not entitled to. That brings everyone else. Today of course, the entire process has been corrupted, with entire industries continuing the process. It is no longer initiated by a few people wanting their freedom.
To me the challenge is not in what is happening outside the urban areas, but what is going on in the urban areas. The modern frontier that needs to be tamed, is the urban frontier. Give those people freedom, and the rest of the problem will take care of itself.